The present invention relates to a seal for a rotary regenerative heat exchanger having a disc type heat accumulator seal and assembly therefore.
Rotary regenerative heat exchangers commonly comprise a housing accommodating therein a disc type heat accumulator containing heat storing material and permitting flow of fluid therethrough from end face to end face. The housing has two fluid stream passages within it; one for hot fluid and another for cold fluid. As the heat accumulator rotates, each section of it passes alternately from a hot fluid stream passage, in which it absorbs heat to a cold fluid stream passage in which it gives up heat to a relatively cold fluid passing through the heat accumulator in the opposite direction. Hot and cold fluids are prevented from mixing with each other by shoes which slidingly and sealingly engage with the end faces of the disc and are mounted on the housing.
Various seals have been used to improve sealing of rotary regenerative heat exchangers including the use of bellows to compensate for relative movement between the shoe and the housing. In this type of seal a thin bellows, a thick shoe and a thick mounting plate are interconnected by welding. The seal thus constructed is mounted in the housing by securing the mouting plate thereto such that the shoe will slidingly contact with the disc type heat accumulator. With this seal, however, upon abrupt temperature variation of the fluid to which the seal is exposed, welded portions either between the mounting plate and the bellows or between the bellows and the shoe are apt to break since the thermal expansion and contraction significantly differs between the thin bellows and the thick shoe and mounting plate. To alleviate this drawback of the prior art mentioned above, there has been proposed a seal which comprises a thin bellows welded at both ends to plates of medium thickness welded to a thick mounting plate and a shoe, respectively. This prior art is not, however, a solution to the drawback mentioned above since the welded portions are not free from breakage when subjected to abrupt temperature variation.